Cat is 고양이， also has 이， seems to be Korean thing. Doesn't work answer of course what it really is...
[The only Wiktionary entry that makes any sense here.]
Etymology 6 Of native Korean origin.
Suffix —이 • (-i)
- a suffix deriving a noun, adding a meaning of a person or an item. -er.
[Incidentally tiger derives from a word meaning sharp, pointed, springy like an arrow so the -er might very well serve the same function . . .]